Currently in the United States, 14 million people suffer from lung disease and/or experience chronic difficulties in breathing. In some instances, such individuals may suffer from diminished oxygen uptake into the body. For example, the lungs of such individuals are not able to sufficiently receive oxygen and discharge carbon dioxide. Regardless of the cause of the pulmonary ailments, even a partial disability of the pulmonary system may require enrichment or supplementation of oxygen gas. The need for oxygen supplementation is particularly acute for persons suffering from Chronic Obstructive Pulmonary Disease (COPD) such as, emphysema and chronic bronchitis. In extreme instances, a severely compromised respiratory system may be incapable of supplying the necessary oxygen level for an individual at rest. As a result, supplemental oxygen must be delivered to such an individual to maintain the amount of oxygen at an acceptable level.
As a result, devices and systems for regulating the delivery of supplemental oxygen are known in the art. Typically, a stationary source of oxygen is provided having a tube attached thereto for supplying oxygen to the individual. For example, the source may be a tank reservoir containing pressurized medical quality oxygen. A flow regulator comprising one or more adjustable valves may be provided at the source to control the rate of oxygen flow from the tank through the tube to deliver oxygen to the patient by way of a nasal cannula, breathing mask, or transtracheal oxygen delivery system.
In general, there are two categories of such gas regulation systems, continuous flow and pulsed flow. As alluded to above, continuous flow devices and systems are generally set at a flow rate that provides the user with sufficient oxygen at all times, regardless of whether the user is inhaling or exhaling. Such continuous flow device and systems are generally described in U.S. Pat. No. 6,467,505 to Thordarson et al. A drawback associated such systems is that that the user only benefits from the supplemental oxygen during times in the respiratory cycle when the patient is inhaling in a manner which enables the supplemental oxygen to reach the lungs. At other times, the supplemental oxygen delivered is of no benefit, and is lost. Thus, when used with pressurized oxygen tanks of finite volume, such systems and devices require more frequent refilling and/or changing of the tanks.
In the alternative, pulsed flow systems may be employed to extend the time that a user may receive oxygen by providing oxygen to a user only when the user inhales. Such devices are described, for example, in U.S. Pat. No. 5,839,464 to Enterline. Typically, a burst of oxygen is delivered into a patient's nasal passages when a patient begins to inhale. This burst of oxygen is often uncomfortable for the patient. In addition, such high flow pulses generally cannot be tailored to the patient's physiological requirements or dynamically adjusted to meet the needs of the patient's changing activity level or breathing pattern. In addition, since the breathing pattern of users with compromised respiratory systems is often erratic, such pulse flow systems may exacerbate the user's breathing difficulties.
In healthy individuals, blood oxygen is regulated through the rate of respiration. With increasing activity level, an individual will breathe faster and/or more deeply to enhance oxygen delivery. Nevertheless, compromised pulmonary systems may be unable to supply the necessary oxygen levels required during increased activity. There is a need to deliver more oxygen to individuals with a compromised pulmonary system during periods of increased activity, i.e., walking to the bathroom, up steps, etc. When a stationary source of oxygen is provided, oxygen delivery rate may be altered by adjusting the oxygen flow at the source prior to undertaking the activity, and returning the oxygen flow rate to a lower level after the activity has been carried out. This is inconvenient when the regulator is out of reach. In addition, when the individual is away from the source, immediately changes the oxygen flow rate cannot be effected. Thus, individuals using this type of stationary gas delivery system often maintains the oxygen flow rate at a higher or lower level than necessary, i.e., during increased activity and at rest, which in turn, may creates a dependency upon the higher oxygen levels that is similar in effect to the use of a habit forming drug.
In some instances, known systems and devices automatically adjust the flow rate of oxygen to a person according to the person's activity level. For example, U.S. Pat. No. 5,928,189 to Phillips et al. describes an activity responsive therapeutic delivery system for delivering oxygen to a person in need of supplemental oxygen. The system is described as responsive to changes in the level of the person's activity. The system includes a source of oxygen, a means for delivering oxygen to a person, and a valve for delivery oxygen from the source to the person at two different flow rates. An activity sensor means is positioned to sense activity of the person, e.g., whether the person is standing or sitting, and to adjust the valve according to the sensed activity. In some instances, e.g., as described in U.S. Pat. No. 6,192,883 to Miller, Jr., the flow rate of oxygen may be adjusted using a manual override.
In addition, the flow of oxygen may be adjusted according to the breathing rate of an individual. For example, U.S. Pat. No. 5,865,174 to Kloeppel describes an apparatus and method that employs a pressure sensor to sense the pressure in the nasal passage of an individual receiving oxygen from a oxygen supply. A controller is provided in operative connection with the sensor. The controller controls a valve connected to the oxygen supply and automatically adjusts the flow rate of oxygen to be adjusted according to the pressure sensed by the sensor. Other examples of such oxygen flow rate regulation are described in U.S. Pat. No. 6,470,885 to Blue et al., U.S. Pat. No. 5,890,490 to Aylsworth et al., U.S. Pat. No. 5,755,224 to Good et al., and U.S. Pat. No. 5,603,315 to Sasso, Jr.,
Systems and devices that automatically adjust the flow rate of oxygen according to a patient's blood oxygen content are also known in the art. For example, U.S. Pat. No. 6,371,114 to Schmidt et al. describes systems for delivering respiratory oxygen to a patient. The system is comprised of a blood oxygen content level sensor (e.g., a pulse oximeter), a supplemental oxygen source, a valve in fluid communication with the supplemental oxygen source, and a controller capable of operating the valve. The controller restricts supplemental oxygen flow through the valve when the blood oxygen content level measured by the blood oxygen content level sensor is above a desired value. U.S. Pat. No. 6,147,149 to Steen provides another example of this type of oxygen flow rate regulator.
One unavoidable drawback of automatically adjustable devices and systems is that they require a sensor for operability. For example, when the sensor is used to monitor the user's respiration, the sensor may be placed in user's nose, elsewhere in the user's respiratory tract, or on the user's face for detecting the flow of oxygen. As another example, when the sensor is used to monitor the user's physical activity, motion sensor detectors often must be placed on or near regions of the user's body engaging in physical activity. As a further example, when the sensor is used to monitor the user's blood oxygen content, invasive techniques for obtaining blood or for positioning the sensor may be required. The sensors generally represent a source of discomfort or irritation for the user.
Another drawback for such devices and systems is that automatic adjustment mechanisms are often imperfect. Often, the response times associated with such mechanisms are inadequate and results in the delayed adjustment of oxygen delivery. For example, when an oximeter is used to measure blood oxygen saturation, a certain amount of time may be needed for blood to circulate to allow oxygen to reach the oximeter. As a result, the delivery of oxygen often fails to reflect the actual demand by user. Because automatic adjustment systems are often associated with pulsed oxygen delivery, such systems may mot be suitable for use by patients with impaired pulmonary system who cannot tolerate pulsed delivery of oxygen.
Thus, there is a need in the art to overcome the shortcomings associated with known gas regulation technology by providing a system for delivering a breathable medical gas that includes a remote control unit to allow a user to adjust the delivery rate of gas flow.